1. Field of the Invention
The present invention relates generally to method and apparatus for the mechanical mixing of fluid samples, and, more particularly, to an assembly having a mechanical mixer positioned within an internal collection chamber of the assembly for maintaining the fluid sample in a homogenous state.
2. Description or the Prior Art
The maintenance of a mixture of solid particles and fluid in a homogeneous state is required for a wide assortment of medical and industrial applications. For example, the need to extract body fluids from an individual for medical testing purposes is well known and widespread. Many apparatus are known in the art for aspirating or otherwise extracting bodily fluids from the subject. Various types of syringe assemblies are disclosed in, for example, U.S. Pat. Nos. 4,384,581; 4,469,482; and 4,713,060. The syringe disclosed in each of the aforementioned patents, as well as many other conventional prior art syringe assemblies include a hypodermic needle of suitable sharpness for puncturing the dermis layer of the subject, and for aspirating a desired bodily fluid from the subject. An end portion of the hypodermic needle is coupled to a collection chamber formed by a barrel portion of the syringe assembly whereat the fluid aspirated by the hypodermic needle is collected. Many syringe assemblies further include a plunger assembly for creating a vacuum to aid in the aspiration of the fluid from the subject.
One such fluid frequently aspirated from a subject for purposes of medical testing is blood. Blood samples of a subject are collected for such purposes as drug and alcohol testing, testing for disease, and detecting the levels of certain blood components. A blood sample from a subject is oftentimes collected for purposes of arterial blood gas analysis for the purpose of testing for cardiac sufficiency. A primary test for cardiac disfunction requires the collection of a blood sample from a subject for purposes of measuring oxygen content of the blood. Cardiac disfunction oftentimes results in the failure of oxygen supply, through blood, to body tissue. In order to insure that a specimen taken from a blood sample is a representative specimen of the blood taken from the subject, the blood sample must be collected under anaerobic conditions, and the blood must be maintained in a homogenous state. Blood is actually comprised of a liquid, plasma portion, and a solid portion consisting of blood cells and platelets. Because the specific gravity of the blood cells and platelets is greater than that of the liquid plasma, the solid portions of the blood mixture tends to settle out of the mixture. When taking specimens of the blood sample, once collected, is in imperative that the blood sample be homogenous in order to insure that a representative specimen is taken from the sample to thereby allow accurate analysis to be performed.
One quick prior art method for maintaining the blood sample in a state of homogeneity is to merely shake the syringe assembly, once the sample has been collected, and the syringe assembly has been removed from the subject. Other prior art apparatus for maintaining the blood sample in homogeneity includes machinery similar to "test-tube shakers" for shaking the blood sample to maintain the solid portions of the blood in solution with the liquid portions thereof.
Although accurate, the mechanical shaking machinery requires an additional step, and, hence, additional time to insure that the blood sample is maintained in a state of homogeneity. And such machinery quite commonly causes trauma and other damage to the blood samples.
Similar devices are used in industry for the research, development and testing of consumer products such as cosmetics, paints, medicines, and the like. Accordingly, such agitator devices suffer from the same shortcomings as their counterparts used in medical laboratories.
It is, accordingly, an object of the present invention to provide a method and apparatus for maintaining a suspension or multilayered fluids to a state of homogeneity to allow accurate testing of representative portions thereof.
It is a further object of the present invention to provide a syringe assembly for the aspiration and collection of a fluid sample, and for mixing the fluid sample, once sedimentation or stratification has developed, to a homogenous state.
It is a yet further object of the present invention to provide apparatus for a syringe assembly for mixing a fluid sample collected in a collection chamber of a syringe assembly to thereby maintain a fluid sample in a homogenous state.
Still other objects and advantages will become apparent in light of the attached drawings and written description of the invention presented herebelow.